Most slug bait at the hardware store is toxic enough to kill your dog.
The active ingredient in standard slug bait is metaldehyde. Less than a teaspoon can poison a 10-pound dog.
Symptoms start within minutes: tremors, seizures, body temperature spiking to 108°F. It also kills cats, birds, frogs, hedgehogs, and any predator that eats a poisoned slug.
The pellets are flavored with molasses to attract slugs. They attract everything else too. The UK banned metaldehyde slug baits for outdoor use in 2022, specifically because of the wildlife and pet deaths.
But the bigger question is why you have a slug problem at all. Slugs and snails are eaten by frogs, toads, ground beetles, fireflies, garter snakes, songbirds, ducks, opossums, and hedgehogs. A yard with predators rarely has a slug crisis.